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POAnalyzing time-dependent, event log from SQL
 

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    <p>I have an event log in a SQL Server database. Essentially it records when a call was made and when that call ended at a call center (as two different records), as well as a few other details. I am trying to get an idea of how many phone lines are being used at any given time with this data. I can't think of any good way to have a SQL query determine this for me, although this would be ideal (if it didn't sacrifice much speed).</p> <p>My first thought was to have a program query the start and end events for each call, determining the duration of the call. I could then step through each unit of time, keeping a tally of how many calls were in progress at any given time. Is there a way I can do this in SQL instead of using a linear method in C# or something similar?</p> <p>Edit: There is a unique ID for the calls. A session ID, if you will. Also, <strong>the start and end events are two different records</strong> -- not a single record. This complicates this a bit I think. Also, this table has over 15 million records in it.</p> <pre><code>Id EvId CallId DateTime -- ---- ------------------------------------ -------------------- 1 0 df1cbc93-5cf3-402a-940b-4441f6a7ec5c 7/9/2008 8:12:56 PM 2 1 df1cbc93-5cf3-402a-940b-4441f6a7ec5c 7/9/2008 8:13:07 PM 3 0 ec1c2078-1765-4377-9126-6f26fe33e4a9 7/10/2008 4:33:10 PM 4 10 ec1c2078-1765-4377-9126-6f26fe33e4a9 7/10/2008 4:33:13 PM 5 1 ec1c2078-1765-4377-9126-6f26fe33e4a9 7/10/2008 4:33:13 PM 6 0 a3c3b9a0-a23b-4dda-b4e4-e82f0209c94d 7/10/2008 4:33:13 PM 7 10 a3c3b9a0-a23b-4dda-b4e4-e82f0209c94d 7/10/2008 4:33:15 PM 8 1 a3c3b9a0-a23b-4dda-b4e4-e82f0209c94d 7/10/2008 4:33:15 PM 9 0 d23f393d-0272-445a-8670-3f71b016174e 7/10/2008 4:33:15 PM 10 10 d23f393d-0272-445a-8670-3f71b016174e 7/10/2008 4:33:17 PM 11 1 d23f393d-0272-445a-8670-3f71b016174e 7/10/2008 4:33:17 PM EvId Description ---- ---------------- 0 New Call 1 End of Call 2 Caller Hangup 10 CPA Completed </code></pre>
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    1. COIs there a unique identifier for each of the calls?
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    2. COTake a look at.http://stackoverflow.com/questions/781895/checking-for-time-range-overlap-the-watchman-problem-sql this shows how to calculate overlaps
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    3. COthere are no "overlapping" calls, some have the same begin/end points. anyway, see my latest edit for sample code...
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